258 LAUKENTIAN EOCKS. 



tian system and those that lie upon it, as the schists and slates of Cambrian, silurian, and 

 Devonian ages, is legitimately called for by the progress of knowledge. 



The area occupied by Laurentian rocks in Vermont is so limited, that it would hardly 

 be worthy of special notice, did it not form so convenient a starting point in the descrip- 

 tion of the geology of the State. We are enabled, with a brief introduction, to commence 

 the description of the oldest rocks on the continent from which relics of animal and vege- 

 table life have been exhumed. According to most geologists, we are ushered from a period 

 of darkness and death to a time of light and life. Standing upon the Laurentian frag- 

 ment, one can see only a waste barren region, destitute of animated existence, scarcely 

 elevated above the shallow ocean, and yet warm from the influence of the primitive globe 

 of molten fire. Ascending a step, and we rest upon a silurian foothold, and the earth 

 appears rejoicing in the vigor of youth, commencing the oft repeated cycles of organic 

 development, which find their perfection in the alluvial period. 



All the Laurentian rocks in Vermont are upon a narrow spur projecting, like an arm, 

 from the great nucleus of older rocks in northern New York. It enters the' town of West 

 Haven directly opposite the terminus of the railroad at the steamboat wharf in Whitehall, 

 and extends three or four miles to the north. It is everywhere quite narrow. The only 

 way of distinguishing the Laurentian character of the deposit is by the higher dip of its 

 strata, upon which* the Potsdam sandstone reposes unconformably. A section passing 

 across the south end of West Haven, in Fig. 168, represents the unconformable relations 

 of the Laurentian rocks and the Potsdam sandstone to each other. Were it not for this 

 discordance in the stratification, we should regard the lower rock as silurian, because it 

 does not differ lithologically from the sandstone above. But in following the strata north- 

 wardly, the quartz rock becomes more gneissoid. Some, of the specimens in the Cabinet, 

 Nos. ifj, ffg and jfg, are very distinct gneiss, one of them with the Labradorite, the 

 characteristic species of feldspar of the Laurentian series. 



We have noticed the following strikes and dips of the strata : 

 Locality. Strike. Dip. Observer. 



Whitehall, N. Y., East of north, 30-40 E., E. H. 



West Haven, southwest corner, East of north, 36 E., C. H. H. and E. H., jr. 



West Haven, do., N. 10 E., 35 E., C. H. H. and E. H., jr. 



West Haven, on Lake Champlain, 17 N. E., C. H. H. 



Garfield's Landing, N. Y., N. 45 E., 25 S. W.', C. H. H. 



Split Eock, N. Y., 34 E., Z. T. 



Probably this range of gneiss has been elevated to its present position, while the cal- 

 ciferous sandrock and Potsdam sandstone upon the west side have not been disturbed, and 

 are now at a lower level than the gneiss, in consequence. As the gneiss rose, the sand- 

 stone overlying it also rose, and now form the range of hills, of which Bald Mountain is 

 the most conspicuous. Consequently we find two different bands of calciferous sandrock, 

 the one east and the other west of the gneiss. The effect of the upheaval is not seen upon 

 the line of the strike of the geniss, in the north part of West Haven, for the calciferous 

 sandrock there entirely covers it, having never been separated into two parts by the 

 elevating agency. 



